Expressions

Two main kinds of expressions that you see:

• postfix expressions (a.k.a. reverse polish notation)
• infix expressions (a.k.a. what we use all the time)

A postfix expression looks like:

5 4 + 8 3 - * 15 /

which, when analyzed left to right, means take 5 and 4 and add them, to get 9, then take 8 and 3 and subtract them, to get 5, and then take the 9 and the 5 and multiply them, to get 45, and then take the 45 and the 15, and divide them to get 3.

This same expression would be written with infix notation, with parentheses, like so:

((5+4)*(8-3))/15